JPH0756441A - Liquid developing device - Google Patents

Abstract

PURPOSE: To reduce the amount of liquid developer deposited on a photoconductive surface in a liquid developing device. CONSTITUTION: The device develops an electrostatic latent image with liquid toner. The device is provided with a liquid extruder 48 forming a liquid image on the photoconductive surface by attracting the electrostatic image and pushing out the thin film of liquid toner. The extruder 48 is electrically biased with appropriate size and polarity so that liquid toner is securely attracted to the electrostatic latent image. Then, vacuum is added to liquid toner for reducing the thickness of a layer coated when liquid toner is attracted to the electrostatic latent image.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to electrophotographic printers, and more particularly to apparatus for developing electrostatic latent images with liquid toner.

[0002]

2. Description of the Related Art U.S. Pat. No. 4,851,317 discloses a toning section having a toner tank containing liquid toner. The toner tank is generally pyramid-shaped and has a V-shaped low area. The low area promotes toner recirculation and eliminates the stagnation area present in the U-shaped tank. The sidewalls of the low area of the tank are preferably sloped so that the toner particles drain to the top of the tank. A toner reservoir is installed inside the tank.
The toner reservoir is preferably electrically isolated. A toning member is supported on the upper edge of the reservoir. The toning member is an L-shaped member that extends across the entire lateral dimension of the imaging member and has an external shape that matches the imaging member so as to cooperate with the imaging member to form a flow path therebetween. The toning member comprises a non-conductive first element and a conductive second element. The first element cooperates with a portion of the side wall of the reservoir to form a channel ending at the orifice. The orifice communicates with the flow path. A centrifugal pump is installed for recirculation of the liquid toner back to the tank via the reservoir. When the toning section is in use, liquid toner flows from the toner tank through the capillaries to the toner reservoir, from the orifices into the channels and over the toning member. The second element is electrically biased. Toning occurs only when there is a bias potential in the area of the channel adjacent to the conductive second element.

US Pat. No. 5,081,499 discloses a liquid developing device in which an electrode is installed on one side of a master. The developing solution is supplied between the master and the electrode. A conductor is in contact with the base of the master to generate an electric field between the master and the electrode to develop the photosensitive layer of the master.

US Pat. No. 5,117,263 discloses a multicolor electrostatic imaging device. An electrostatic latent image is recorded on the photoconductive drum. An electrically biased developer roller is located spaced from the photoconductive drum. Directly into a part of the developing roller, part of the photoconductive drum, or directly into the development area between the photoconductive drum and the developing roller, a multicolor liquid developer spraying device applies liquid toner containing charged colored toner particles. To spray. The color-specific cleaning blade, which is operatively associated with the developing roller, individually removes the residue of each color toner remaining on the developing roller after development. When the toner of the corresponding color is supplied to the developing area by the spraying device, each blade selectively contacts the developing roller. The multicolor toner spray device has a linear array of spray ports. Each spray port is connected to a conduit that supplies colored liquid toner from a corresponding reservoir. The spray ports are combined such that when four colors are used, each fourth spray port sprays the same color toner and four adjacent spray ports spray four different colors. Each color toner is pressurized and sprayed from each spray port onto the developing area. To make the toner fill the development area almost uniformly for each color,
The spacing of the spray ports and their periodicity are selected. In this way, the latent image is developed in liquid color.

[0005]

In conventional liquid development, in which the rotary developing roller is dipped in a liquid and the electrodes are used to create the necessary electric field between the developing roller and the photoconductive surface, an inter-original gap or non-original gap is used. The entire length of the photoconductive surface, including the imaged areas, is always coated with liquid developer. This wastes the developer and significantly increases the load on the cleaning device of the printing press. Therefore, it is desirable to reduce the amount of liquid developer deposited on the photoconductive surface.

[0006]

As a first aspect, the present invention provides an apparatus for developing an electrostatic latent image with liquid toner. The developing device includes a member including a lip configured to supply liquid toner to the latent image for developing the latent image with a layer of liquid toner, and a member on the latent image when the member applies the liquid toner to the latent image. Means are provided to reduce the pressure on the liquid toner to reduce the thickness of the liquid toner.

As a second aspect of the present invention, there are provided an image forming surface, means for recording an electrostatic latent image on the image forming surface, and means for developing the electrostatic latent image recorded on the image forming surface with liquid toner. An electrostatic printing machine having the same is provided. The developing means is a member including a lip configured to supply liquid toner to the latent image for developing the latent image with a layer of liquid toner, the lip electrically for attracting the liquid toner from the lip to the electrostatic latent image. And biasing means and means for reducing the pressure on the liquid toner to reduce the thickness of the liquid toner on the latent image when the member applies the liquid toner to the latent image.

As a third aspect of the present invention, an image forming surface, means for recording a plurality of electrostatic latent images on the image forming surface, and liquids of different colors for each electrostatic latent image recorded on the image forming surface. A multicolor electrostatic printer having means for developing with toner is provided. The developing means includes a plurality of members each including a lip configured to supply the liquid toner to the latent image so that each member develops the latent image with the layer of the liquid toner, and the member includes the liquid toner to the latent image. A means for lowering the pressure applied to the liquid toner in order to reduce the thickness of the liquid toner on the latent image when applying is provided.

Other features of the present invention will become apparent when the following description is read with reference to the accompanying parts.

[0010]

EXAMPLES Various examples will be described below, but it will be understood that the present invention is not limited to these examples. The present invention is intended to embrace all alternatives, modifications and equivalents included within the spirit and scope of the invention as claimed.

For a general understanding of the features of the present invention, reference will be made to the drawings. Throughout the drawings, the same components are designated by the same reference numerals. FIG. 7 shows an electrophotographic printing machine incorporating the features of the present invention. It will be apparent from the following description that the liquid developing apparatus of the present invention can be equally used in various types of printing machines, and its use is not necessarily limited to the particular embodiments described.

The electrophotographic printing machine shown in FIG. 7 uses a drum 10 having a photoconductive surface 12 rotatably mounted within the printing machine. Photoconductive surface 12 is drum 1
It surrounds the outer circumference of 0. A series of processing units are arranged around the drum 10 and as the drum 10 rotates in the direction of arrow 14, the drums sequentially pass through the processing units. The drum 10 is driven by a drive motor at a predetermined speed with respect to other operating mechanisms. In order to synchronize various operations of the copying machine with the rotation of the drum 10,
The timing detector detects the rotation of the drum 10 and sends an output signal to the logic circuit. In this way, the events occur in the correct order in each processor.

First, the drum 10 rotates the photoconductive surface 12 to pass the charging section A. At charging station A, corona generator 16 sprays ions onto photoconductive surface 12 to uniformly generate a relatively high charge on surface 12.

The drum 10 then rotates the charged photoconductive surface to the exposure station B. At the exposure station B, the light image of the original document is projected onto the charged portion of the photoconductive surface 12. The exposure section B has a moving lens system 18. The original document 20 is placed face down on a flat transparent platen 22. The lamp 24 moves in time with the lens 18,
It is adapted to scan successive incremental areas of the original document 20. Thus, the flowing light image of original document 20 is projected onto the charged portions of photoconductive surface 12. This selectively erases the charge on photoconductive surface 12 and records an electrostatic latent image on photoconductive surface 12 corresponding to the informational areas of original document 20. To optically filter the light image, a selected optical filter (not shown) having a color complementary to the color of each liquid toner is placed in the optical path. Although optical lens systems have been described above, it should be understood that other methods, such as a raster output scanner, can be used to record an electrostatic latent image by discharging selected areas of the photoconductive surface with a modulated laser beam. Ah

After exposure, drum 10 rotates the electrostatic latent image recorded on photoconductive surface 12 to development station C. In the developing section C, a plurality of developing units 26, 28, 30, 32 are installed. The developing units are substantially the same as each other, and the details thereof will be described later with reference to FIGS.
Each developing unit pushes a liquid developer onto the electrostatic latent image to develop the electrostatic latent image with toner particles of the corresponding color. For example, the developing unit 26 pushes cyan liquid toner, the developing unit 28 pushes magenta liquid toner, the developing unit 30 pushes yellow liquid toner, and the developing unit 32 pushes black liquid toner. In operation, a filter is used in conjunction with lens 18 to direct light of a selected color onto photoconductive surface 12 to selectively discharge a portion thereof. For example, a red filter is used to discharge selected areas with charged areas that are developed with a red subtractive primary or cyan liquid toner. Therefore, when a red filter is used in conjunction with lens 18, developing unit 26 develops the charged areas with cyan liquid toner. Similarly, when the green filter is used, the developing unit 28 develops the area charged with the magenta liquid toner. When the blue filter is used, the developing unit 30 selectively develops the area charged with the yellow liquid toner. Finally, for those areas of the original document that are desired to be reproduced in black, developer unit 32 develops the areas charged with black liquid toner. Each development unit is selectively activated during repeated cycles. This means that the developing unit 26 is activated during the first cycle using the red filter. Subsequently, the developing unit 28 is activated during the second cycle using the green filter. The developing unit 30 is activated during the third cycle using the blue filter. Finally, the developing unit 32 is activated during the fourth cycle.

Each liquid image can be transferred to a copy sheet after each cycle, or successive liquid images can be developed on top of one another on photoconductive surface 12 to form a composite multicolor liquid image. You can also This composite multicolor liquid image can be transferred to the copy sheet 34 after the fourth cycle.

In the electrophotographic printing machine shown in FIG. 7,
A multicolor liquid toner image or composite toner image is formed on the photoconductive surface 12 and then transferred to a copy sheet. This composite toner image is transferred at the transfer section D.

In the transfer section D, the composite multicolor liquid toner image is transferred to the copy sheet 34. Prior to transferring the multicolor liquid toner image to copy sheet 34, conditioning roller 36 contacts the composite multicolor liquid toner image. For example, conditioning roller 36 is an electrically biased squeegee roller that is pressed against the surface of drum 10 to remove liquid carrier from the background areas and compress the image in the image areas to remove liquid carrier from the image. May be. The squeegee roller 36 is preferably made of a polymer material having elasticity and having some conductivity. Squeegee roller 3
6 is charged to a potential of hundreds to thousands of volts with the same polarity as the charge on the toner particles. The composite multicolor liquid toner image is conditioned and then proceeds to transfer station D. Transfer roller 38 is maintained at an appropriate voltage and temperature to electrostatically transfer the image from photoconductive surface 12 to copy sheet 34. The transfer roller 38 is preferably pressurized and electrically biased to ensure transfer of the composite multicolor liquid toner image to the copy sheet 34.

The composite multicolor liquid toner image is transferred to the copy sheet 34.
After being transferred to, the copy sheet is conveyed by the conveyor 40,
It passes through the fixing section E. The fusing station E has a radiant heater 42 that radiates sufficient heat energy to permanently fuse the toner to the copy sheet 34 in the image. Conveyor 40 feeds copy sheet 34 in the direction of arrow 44 through radiant heater 42 to catch tray 46. The operator can easily take out the copy sheet 34 placed on the catch tray 46.

Continuing with the description of FIG. 7, after transferring the liquid toner image to the copy sheet 34, some residual liquid toner will always remain attached to the photoconductive surface 12 of the drum 10. This residue is removed from the photoconductive surface 12 at the cleaning station F.
Removed from. The cleaning unit F includes a soft elastic blade 68. The blade has its free end in contact with the photoconductive surface 12 and removes any material that may have deposited on it. After cleaning, the lamp 70 is turned on to discharge any residual charge on the photoconductive surface 12 prior to the next successive imaging cycle. In this way, a continuous electrostatic latent image can be developed.

The developing device of the present invention can be used in a multicolor electrophotographic printing machine or a single color printing machine.
The developed image can be transferred directly to a copy sheet or can be transferred to an intermediate member prior to transfer to the copy sheet. Multicolor printers can use this type of developing unit to develop a continuous latent image to form a composite multicolor toner image and then transfer it to a copy sheet or, instead, a single color liquid image. It is also possible to transfer the images directly onto the copy sheet by superimposing them on each other.

The above is the description of the general operation of the electrophotographic printer including the developing device of the present invention. Next, FIGS.
The detailed structure of the developing device will be described with reference to FIG.

As shown in FIG. 1, the liquid extruder 48 has a first
It comprises a member 50 and a second member 52. First member 50
The open channel 54 is made in the
A distribution channel 56 extends transversely. A plurality of distribution channels are arranged along the longitudinal axis of the drum 10. The above is clearly shown in FIG. As shown in FIG. 2, the first portion 54a of the distribution channel 54
Is connected to a source of liquid developer. The second and third portions 54b, 54c of the distribution channel 54 are approximately V
It intersects the first portion 54a in a letter shape, forming a Y-shaped channel. Distribution channels 5 arranged at equal intervals
6 is the second and third portions 54b, 54 of the channel 54
It intersects with c. Distribution channel 56 is channel 5
4 receives liquid developer and guides it to lip 58.
Channels 54b, 54c for distribution channel 56
The angle of inclination ensures that the lip 58 is coated with a thin film liquid developer having straight leading and trailing edges. The angle of inclination and the cross-sectional diameter of the channels ensure that liquid developer is substantially evenly distributed along lip 58. Lip is drum 1
The surface 58 of the second member 52 is parallel to the vertical axis of 0 and forms a gap with the drum 10. The gap between the lip 58 and the drum 10 is the surface 60 of the first member 50 and the drum 10.
Narrower than the gap between. Lip 58 is used to apply a uniform thickness of liquid developer to the electrostatic latent image recorded on photoconductive surface 12 of drum 10. In order to deliver the required amount of liquid developer for each electrostatic latent image from the source to the extruder 48,
A metering pump is used.

FIG. 3 shows an alternative embodiment of the channel arrangement within liquid extruder 48. As shown, channel 62
Is connected to a liquid developer supply, and distribution channel 56 runs diagonally across channel 62. Again, the slope of channel 62 relative to distribution channel 56 is designed to ensure that the liquid developer covers lip 58 with a thin film having straight leading and trailing edges.

FIG. 4 shows a vacuum pump 64 configured to apply a vacuum upstream of the liquid extruder 48. The vacuum pump 64 reduces the pressure applied to the liquid, that is, sucks the liquid toner upward. Photoconductive surface 12 of drum 10
By applying a vacuum to the liquid developer being applied to the, the gap between the lip 58 and the photoconductive surface 12 is made larger,
A coating of the same thickness can be obtained on the photoconductive surface 12. For example, the gap between the lip 58 and the photoconductive surface 12 can be up to several times the thickness of the developer layer coated on the photoconductive surface 12. The liquid developer thin film thickness can be 1 mil or less. This is lip 58
The tolerance of the gap between the photoconductive surface 12 and the photoconductive surface 12 is significantly reduced. The liquid extruder 48 is electrically biased to the appropriate value and polarity by a voltage source 66 to ensure that the electrostatic latent image recorded on the photoconductive surface 12 attracts the liquid developer.

As shown in FIG. 5, a plurality of liquid extruders 48
It is possible to connect one vacuum pump 64 to. Furthermore, it should be noted that when using multiple liquid extruders 48, only one first member 50 is required. Therefore, in the first extruder 48, the first member 50 is coupled to the second member 52. In the next extruder, since the lower part of the second member 52 functions as the first member 50 with the same volume, the first member 5
0 is unnecessary. As a result, the size of the developing unit is reduced and the structure is simplified.

For multiple colors, multiple liquid extruders can be used. As shown in FIG. 6, the developing unit 26
The uppermost liquid extruder 48, which comprises the above, has both a first member 50 and a second member 52. Developing units 28, 30, 3
The second remaining liquid extruder 48 requires a second member 52.
Only. Since successive liquid toner images are deposited on top of each other on photoconductive surface 12 of drum 10,
The gap between the lip 58 and the surface of the liquid toner gradually narrows. To maintain this gap constant, the gap between successive lips must be offset with respect to the photoconductive surface 12. Thus, the continuous lip 58 and the photoconductive surface 12
The gap between and increases in the moving direction 14 of the drum 10.
As shown in FIG. 6, the gap g ₄ is larger than the gap g _3, the gap g ₃ is larger than the gap g _2, the gap g ₂ is greater than the gap g _1.

A multicolor development unit using the liquid extruder 48 can be made about 1 inch high. Therefore, it can be seen that a compact multicolor developing device can be realized by using the liquid extruder of the present invention.

[0029]

The developing unit of the present invention comprises a first member and a second member.
It has a liquid extruder composed of members. A supply channel is connected to the pump that carries the liquid toner from the source to the distribution channel. The distribution channel carries liquid toner to the lip. The lip is a surface parallel to the longitudinal axis of the photoconductive drum. A uniform layer of liquid toner is metered onto the electrostatic latent image. To ensure that the electrostatic latent image attracts liquid toner,
The liquid extruder is electrically biased to the proper potential and polarity. This greatly eases the gap tolerance between the lip and the photoconductive surface.

From the foregoing, it is apparent that an apparatus for developing an electrostatic latent image with liquid toner has been provided according to the present invention. The device fully achieves the objects and advantages mentioned above. Although the present invention has been described in terms of particular embodiments, it will be apparent to those skilled in the art that many alternatives, modifications and equivalents are readily envisioned. Therefore, the present invention is intended to include all alternatives, modifications and equivalents within the spirit and broad scope of the invention described in the claims.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view of a liquid extruder incorporating features of the present invention.

FIG. 2 is a plan view of an embodiment of the liquid extruder shown in FIG.

3 is a plan view of an alternative embodiment of the liquid extruder of FIG.

FIG. 4 is a partial sectional front view showing a vacuum device and a voltage source connected to the liquid extruder of FIG.

FIG. 5 is a partial sectional front view showing a vacuum device connected to a plurality of liquid extruders.

FIG. 6 is a partial cross-sectional front view showing a plurality of liquid extruders used in a multicolor printing machine.

FIG. 7 is a schematic illustration of a multicolor electrophotographic printing machine using the liquid extruder of FIGS. 1-6.

[Explanation of symbols]

 A charging unit B image forming unit C developing unit D transfer unit E fixing unit F cleaning unit 10 drum 12 photoconductive surface 14 rotation direction 16 corona generating device 18 moving lens system 20 original document 22 transparent platen 24 lamps 26, 28, 30 , 32 Development unit 34 Copy sheet 36 Conditioning roller 38 Transfer roller 40 Conveyor 42 Radial fixing device 44 Moving direction 46 Catch tray 48 Liquid extruder 50 First member 52 Second member 54 Supply channel 56 Distribution channel 58 Lip 60 First member Surface 62 Channel 64 Vacuum pump 66 Voltage source 68 Cleaning blade 70 Lamp

Claims (2)

[Claims] 1. An apparatus for developing an electrostatic latent image with liquid toner, the member comprising a lip configured to supply liquid toner to the latent image for developing the latent image with a layer of liquid toner. A developing device, comprising means for lowering the pressure applied to the liquid toner in order to reduce the thickness of the liquid toner on the latent image when the member applies the liquid toner to the latent image. 2. The developing device according to claim 1, further comprising means for electrically biasing the lip to attract liquid toner from the lip to the latent image.